Method of manufacturing light-emitting device including phosphor pieces

ABSTRACT

A method of manufacturing a light-emitting device  1  includes a step of providing first phosphor sheets  11 , a step of providing second phosphor sheets  12 , a step of providing a light-emitting element  13 , a selection step of selecting a combination of one of the first phosphor sheets  11  and one of the second phosphor sheets  12  on the basis of a wavelength conversion characteristic of each of the first phosphor sheets  11  and a wavelength conversion characteristic of each of the second phosphor sheets  12 , a step of obtaining a plurality of first phosphor pieces  11   c  and a plurality of second phosphor pieces  12   c  from the selected first phosphor sheet  11  and the selected second phosphor sheet  12 , and a step of disposing one of the first phosphor pieces  11   c  and one of the second phosphor pieces  12   c  on or above the light-emitting element  13.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2019-111831, filed on Jun. 17,2019; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments relate to a method of manufacturing a light-emitting device.

BACKGROUND

Light-emitting devices employing combinations of light-emitting elementsand phosphor sheets have been developed in recent years. For example, alight-emitting device that emits white light as a whole can be providedby disposing, on a light-emitting element that emits blue light, aphosphor sheet that absorbs blue light to emit green light and aphosphor sheet that absorbs blue light to emit red light in layers.Characteristics of light emitted from such a light-emitting device mayvary due to variation in characteristics of the phosphor sheets.

SUMMARY

A method of manufacturing a light-emitting device according to oneembodiment of the present invention includes: providing a plurality offirst phosphor sheets; providing a plurality of second phosphor sheets;providing a light-emitting element; selecting a combination of one ofthe first phosphor sheets and one of the second phosphor sheets on thebasis of a wavelength conversion characteristic of each of the firstphosphor sheets and a wavelength conversion characteristic of each ofthe second phosphor sheets, a step of obtaining a plurality of firstphosphor pieces and a plurality of second phosphor pieces from theselected first phosphor sheet and the selected second phosphor sheet;and disposing one of the first phosphor pieces and one of the secondphosphor pieces on or above the light-emitting element.

A method of manufacturing a light-emitting device according to anotherembodiment of the present invention includes: providing a plurality offirst phosphor sheets; providing a plurality of second phosphor sheets;providing a plurality of light-emitting elements; selecting acombination of one of the first phosphor sheets and one of the secondphosphor sheets on the basis of a wavelength conversion characteristicof each of the first phosphor sheets and a wavelength conversioncharacteristic of each of the second phosphor sheets; disposing theplurality of light-emitting elements on or above a layered sheet inwhich the selected first phosphor sheet and the selected second phosphorsheet are layered; and dividing the layered sheet.

A method of manufacturing a light-emitting device according to stillanother embodiment of the present invention includes: providing aplurality of first phosphor sheets; providing a plurality of secondphosphor sheets; providing a light-emitting element; selecting acombination of one of the first phosphor sheets and one of the secondphosphor sheets on the basis of a wavelength conversion characteristicof each of the first phosphor sheets and a wavelength conversioncharacteristic of each of the second phosphor sheets; and disposing theselected first phosphor sheet and the selected second phosphor sheet ata position capable of receiving light emitted from the light-emittingelement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method of manufacturing a light-emittingdevice according to a first embodiment.

FIG. 2A is a schematic perspective view of first phosphor sheets used inthe first embodiment.

FIG. 2B is a schematic cross-sectional view of one of the first phosphorsheets used in the first embodiment.

FIG. 3A is a schematic perspective view of second phosphor sheets usedin the first embodiment.

FIG. 3B is a schematic cross-sectional view of one of the secondphosphor sheets used in the first embodiment.

FIG. 4A is a graph which shows a method of classifying the firstphosphor sheets according to x value, and in which the horizontal axisshows x value of xy chromaticities, and the vertical axis shows count.

FIG. 4B is a graph which shows a method of classifying the secondphosphor sheets according to y value, and in which the horizontal axisshows y value of xy chromaticities, and the vertical axis shows count.

FIG. 5A is an xy chromaticity diagram for a method of selecting thefirst phosphor sheet and the second phosphor sheet in the firstembodiment.

FIG. 5B is an xy chromaticity diagram for the method of selecting thefirst phosphor sheet and the second phosphor sheet in the firstembodiment.

FIG. 6 schematically shows a step of obtaining first phosphor pieces andsecond phosphor pieces from the first phosphor sheet and the secondphosphor sheet.

FIG. 7 is a schematic cross-sectional view of the light-emitting deviceaccording to the first embodiment.

FIG. 8 is an xy chromaticity diagram showing the chromaticitydistribution of light emitted from the light-emitting device accordingto the first embodiment.

FIG. 9 is an xy chromaticity diagram showing the chromaticitydistribution of light emitted from the light-emitting device accordingto the first embodiment.

FIG. 10A schematically shows a method of manufacturing a light-emittingdevice according to a first modified example of the first embodiment.

FIG. 10B schematically shows the method of manufacturing alight-emitting device according to the first modified example of thefirst embodiment.

FIG. 11 is an xy chromaticity diagram for a method of selecting thefirst phosphor sheet and the second phosphor sheet in a second modifiedexample of the first embodiment.

FIG. 12 is an xy chromaticity diagram showing simulation results in thecase in which the first phosphor sheets and the second phosphor sheetsare respectively combined.

FIG. 13 is a flowchart of a method of manufacturing a light-emittingdevice according to a second embodiment.

FIG. 14A is a schematic cross-sectional view for illustrating the methodof manufacturing a light-emitting device according to the secondembodiment.

FIG. 14B is a schematic cross-sectional view for illustrating the methodof manufacturing a light-emitting device according to the secondembodiment.

FIG. 15 is a flowchart of a method of manufacturing a light-emittingdevice according to a third embodiment.

FIG. 16 is a schematic cross-sectional view of the light-emitting deviceaccording to the third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention and their modified examples will bedescribed below. In the embodiments and their modified examples otherthan a first embodiment, only features different from the features ofthe first embodiment will be generally described, and otherconstitutions, effects are substantially the same as in the firstembodiment. The embodiments and the modified examples can be combinedwith one another. Further, drawings used for description are schematicand simplified as appropriate.

First Embodiment

FIG. 1 is a flowchart of a method of manufacturing a light-emittingdevice according to the present embodiment.

FIG. 2A is a schematic perspective view of first phosphor sheets used inthe present embodiment, and FIG. 2B is a schematic cross-sectional viewof one of the first phosphor sheets.

FIG. 3A is a schematic perspective view of second phosphor sheets usedin the present embodiment, and FIG. 3B is a schematic cross-sectionalview of one of the second phosphor sheets.

FIG. 4A is a graph which shows a method of classifying the firstphosphor sheets according to x value, and in which the horizontal axisshows x value of xy chromaticities, and the vertical axis shows count.FIG. 4B is a graph which shows a method of classifying the secondphosphor sheets according to y value, and in which the horizontal axisshows y value of xy chromaticities, and the vertical axis shows count.

FIG. 5A and FIG. 5B are xy chromaticity diagrams for a method ofselecting the first phosphor sheet and the second phosphor sheet in thepresent embodiment.

FIG. 6 schematically shows a step of obtaining first phosphor pieces andsecond phosphor pieces from the first phosphor sheet and the secondphosphor sheet.

FIG. 7 is a schematic cross-sectional view of the light-emitting deviceaccording to the present embodiment.

A plurality of first phosphor sheets 11 are first provided in Step S1 inFIG. 1 as shown in FIG. 2A. The first phosphor sheets 11 may be providedby manufacturing or purchasing the sheets. As shown in FIG. 2B, a largenumber of particles of a first phosphor 11 b are dispersed in a firstbase material 11 a made of a transparent resin material in each of thefirst phosphor sheets 11. The first phosphor 11 b absorbs first light L1to emit second light L2. For example, the first light L1 is blue light,and the second light L2 is red light. In an example, the first phosphor11 b is a fluoride phosphor such as KSF (K₂SiF₆:Mn⁴⁺). Regarding aplurality of first phosphor sheets 11, the thickness of the firstphosphor sheet 11, the distribution density of the first phosphor 11 b,and the like unavoidably vary.

A plurality of second phosphor sheets 12 are also provided in Step S2 inFIG. 1 as shown in FIG. 3A. The second phosphor sheets 12 may also beprovided by manufacturing or purchasing the sheets. As shown in FIG. 3B,a large number of particles of a second phosphor 12 b are dispersed in asecond base material 12 a made of a transparent resin material in eachof the second phosphor sheets 12. The second phosphor 12 b absorbs thefirst light L1 to emit third light L3. For example, the third light L3is green light. In an example, the second phosphor 12 b is a β-SiAlON(Si_(6-z)Al_(z)O_(z)N_(8-z):Eu²⁺). Also regarding a plurality of secondphosphor sheets 12, the thickness of the second phosphor sheet 12, thedistribution density of the second phosphor 12 b, and the likeunavoidably vary.

Further, a light-emitting element 13 is provided in Step S3 in FIG. 1.The light-emitting element 13 may also be provided by manufacturing orpurchasing the light-emitting element. The light-emitting element 13emits the first light L1. Examples of the light-emitting element 13include a light-emitting diode (LED). The order of Step S1 of providinga plurality of first phosphor sheets 11, Step S2 of providing aplurality of second phosphor sheets 12, and Step S3 of providing alight-emitting element 13 is not limited to a particular order.

Next, a wavelength conversion characteristic of each of the firstphosphor sheets 11 provided in Step S1 is measured in Step S4 in FIG. 1.For example, the chromaticity is measured as an example of thewavelength conversion characteristic. Specifically, a predeterminedregion of each first phosphor sheet 11 is radiated with excitationlight. The excitation light is the first light L1 or light with a peakwavelength close to the peak wavelength of the first light L1. The firstphosphor 11 b of the first phosphor sheet 11 is thus excited byabsorption of the excitation light to emit the second light L2.Accordingly, the first phosphor sheet 11 emits the mixed light of theexcitation light and the second light L2. The chromaticity (firstchromaticity) of the mixed light is measured. The first chromaticity is,for example, a set of an x value and a y value in the XYZ colorimetricsystem. The first chromaticity unavoidably varies because of variationin the thickness of the first phosphor sheet 11 and variation in thedistribution density of the first phosphor 11 b.

Next, the first phosphor sheets 11 are classified according to x valueof the first chromaticity in Step S5 in FIG. 1 as shown in FIG. 4A. Forexample, in the case in which the specification range of the x value ofthe first phosphor sheet 11 is x1 or more and x2 or less, a criterionvalue x0 greater than x1 and less than x2 is set. In the case in whichthe x value of a first phosphor sheet 11 is x1 or more and x0 or less,the first phosphor sheet 11 is classified as a first group G1. On theother hand, in the case in which the x value of another first phosphorsheet 11 is greater than x0 and x2 or less, the first phosphor sheet 11is classified as a second group G2.

The criterion value x0 can be, for example, the average value of the xvalues of the first phosphor sheets 11 provided in Step S1.Alternatively, the criterion value x0 may be the intermediate valuebetween the lower limit x1 and the upper limit x2 of the specificationrange of the x value. That is, x0=(x1+x2)/2 may be employed.Alternatively, the criterion value x0 may be the median of the x valuesof the first phosphor sheets 11 provided in Step S1.

Similarly, a wavelength conversion characteristic of each of the secondphosphor sheets 12 provided in Step S2 is measured in Step S6 in FIG. 1.For example, the chromaticity is measured as an example of thewavelength conversion characteristic. Specifically, a predeterminedregion of each second phosphor sheet 12 is radiated with excitationlight. For example, the same excitation light as the light used for themeasurement of the wavelength conversion characteristic of the firstphosphor sheet 11 in Step S4 is used as the excitation light. The secondphosphor 12 b of the second phosphor sheet 12 is thus excited byabsorption of the excitation light to emit the third light L3.Accordingly, the second phosphor sheet 12 emits the mixed light of theexcitation light and the third light L3. The chromaticity (secondchromaticity) of the mixed light is measured. The second chromaticityis, for example, a set of an x value and a y value in the XYZcolorimetric system. The second chromaticity unavoidably varies becauseof variation in the thickness of the second phosphor sheet 12 andvariation in the distribution density of the second phosphor 12 b.

Next, the second phosphor sheets 12 are classified according to y valueof the second chromaticity in Step S7 in FIG. 1 as shown in FIG. 4B. Forexample, in the case in which the specification range of the y value ofthe second phosphor sheet 12 is y1 or more and y2 or less, a criterionvalue y0 greater than y1 and less than y2 is set. In the case in whichthe y value of a second phosphor sheet 12 is y1 or more and y0 or less,the second phosphor sheet 12 is classified as a third group G3. On theother hand, in the case in which the y value of another second phosphorsheet 12 is greater than y0 and y2 or less, the second phosphor sheet 12is classified as a fourth group G4.

The criterion value y0 can be, for example, the average value of the yvalues of the second phosphor sheets 12 provided in Step S2.Alternatively, the criterion value y0 may be the intermediate valuebetween the lower limit y1 and the upper limit y2 of the specificationrange of they value. That is, y0=(y1+y2)/2 may be employed.Alternatively, the criterion value y0 may be the median of the y valuesof the second phosphor sheets 12 provided in Step S2.

Next, a combination of a first phosphor sheet 11 and a second phosphorsheet 12 is selected on the basis of the wavelength conversioncharacteristic of each first phosphor sheet 11 and the wavelengthconversion characteristic of each second phosphor sheet 12 in Step S8 inFIG. 1.

Specifically, a first phosphor sheet 11 classified as the first group G1in Step S5 and a second phosphor sheet 12 classified as the fourth groupG4 in Step S7 are combined as shown in FIG. 5A. Also, a first phosphorsheet 11 classified as the second group G2 in Step S5 and a secondphosphor sheet 12 classified as the third group G3 are combined as shownin FIG. 5B.

Next, a plurality of first phosphor pieces 11 c and a plurality ofsecond phosphor pieces 12 c are respectively obtained from the selectedfirst phosphor sheet 11 and the selected second phosphor sheet 12 inStep S9 in FIG. 1 as shown in FIG. 6. For example, the first phosphorsheet 11 and the second phosphor sheet 12 are layered to form a singlesheet, and the sheet is then divided.

Next, in Step S10 in FIG. 1, a second phosphor piece 12 c and a firstphosphor piece 11 c are disposed on the light-emitting element 13provided in Step S3 as shown in FIG. 7. A light-emitting device 1 isthus manufactured.

In the light-emitting device 1, the second phosphor piece 12 c and thefirst phosphor piece 11 c are layered on the light-emitting element 13.The light-emitting element 13 emits, for example, blue first light L1.The second phosphor piece 12 c absorbs a portion of the first light L1to emit, for example, green third light L3. The first phosphor piece 11c absorbs another portion of the first light L1 and a portion of thethird light L3 to emit, for example, red second light L2. Thelight-emitting device 1 therefore emits the mixed light of the firstlight L1, the second light L2, and the third light L3. The mixed lightis, for example, white light.

Next, the effects of the present embodiment will be described.

FIG. 8 and FIG. 9 are xy chromaticity diagrams showing the chromaticitydistributions of light emitted from the light-emitting device accordingto the present embodiment.

The combination of the first phosphor piece 11 c and the second phosphorpiece 12 c in the light-emitting device 1 is the combination of a firstphosphor piece 11 c in the first group G1 and a second phosphor piece 12c in the fourth group G4 or the combination of a first phosphor piece 11c in the second group G2 and a second phosphor piece 12 c in the thirdgroup G3. Hence, the chromaticity coordinates of light emitted from thelight-emitting device 1 fall within a region R1 of x values of x1 ormore and x0 or less and y values of greater than y0 and y2 or less orwithin a region R2 of x values of greater than x0 and x2 or less and yvalues of y1 or more and y0 or less as shown in FIG. 8.

On the other hand, if first phosphor pieces 11 c and second phosphorpieces 12 c within specification ranges are randomly combined withoutperforming Steps S4 to S8, the chromaticity coordinates of light emittedfrom the light-emitting device are distributed in a region R3 of xvalues of x1 or more and x2 or less and y values of y1 or more and y2 orless. In the xy chromaticity diagram, the area of the region R3 isgreater than the sum of the area of the region R1 and the area of theregion R2. As described above, the range of variation of thechromaticity coordinates of light emitted from the light-emitting device1 can be reduced in the present embodiment. Accordingly, thecharacteristics of light emitted from the light-emitting device 1 can bemade uniform.

As described above, the criterion value x0 may be the intermediate valuebetween the lower limit x1 and the upper limit x2 of the specificationrange of the x value. Similarly, the criterion value y0 may be theintermediate value between the lower limit y1 and the upper limit y2 ofthe specification range of the y value.

As described above, the criterion value x0 may be the median of the xvalues of the first phosphor sheets 11. Similarly, the criterion valuey0 may be the median of the y values of the second phosphor sheets 12.The number of the first phosphor sheets 11 classified as the group G1can thus be substantially equal to the number of the first phosphorsheets 11 classified as the group G2 when a plurality of first phosphorsheets 11 are classified into the group G1 and the group G2. Similarly,the number of the second phosphor sheets 12 classified as the group G3can be substantially equal to the number of the second phosphor sheets12 classified as the group G4 when a plurality of second phosphor sheets12 are classified into the group G3 and the group G4.

In the case in which the criterion value is the median, the chromaticitycoordinates of light emitted from the light-emitting device 1 aredistributed in the region R1 and the region R2 as shown in FIG. 8 if thedistribution of the x values shown in FIG. 4A and the distribution ofthe y values shown in FIG. 4B are normal distributions. However, in thecase in which the distributions of the x values and the y values are notnormal distributions but are distorted distributions, the chromaticitycoordinates of light emitted from the light-emitting device 1 fallwithin a hexagonal region R4 with a first point P1 (xp1,y1), a secondpoint P2 (x2,y1), a third point P3 (x2,yp3), a fourth point P4 (xp4,y2),a fifth point P5 (x1,y2), and a sixth point P6 (x1,yp6) at its verticesin the xy chromaticity diagram as shown in FIG. 9. The values xp1 andxp4 are greater than x1 and less than x2 and are not necessarily theintermediate value between the lower limit x1 and the upper limit x2.The values yp3 and yp6 are greater than y1 and less than y2 and are notnecessarily the intermediate value between the lower limit y1 and theupper limit y2. Also in this case, the characteristics of light emittedfrom the light-emitting device 1 can be more uniform than in the case inwhich first phosphor pieces 11 c and second phosphor pieces 12 c arerandomly combined.

First Modified Example of First Embodiment

FIG. 10A and FIG. 10B schematically show a method of manufacturing alight-emitting device according to the present modified example.

The first chromaticities in a plurality of regions of each firstphosphor sheet 11 as shown in FIG. 10A are measured, and the averagevalue of the first chromaticities in the regions is assumed to be thefirst chromaticity of the first phosphor sheet 11 in Step S4 ofmeasuring first chromaticities of the first phosphor sheets 11 in FIG. 1in the present modified example.

For example, a total of nine regions consisting of a central portion 11d, middle portions 11 e of the four sides, and four corners 11 f of asingle first phosphor sheet 11 are radiated with the excitation light tomeasure the chromaticity in each region. The average value of themeasured values is assumed to be the chromaticity (first chromaticity)of the first phosphor sheet 11.

Similarly, the second chromaticities in a plurality of regions of eachsecond phosphor sheet 12 as shown in FIG. 10B are measured, and theaverage value of the second chromaticities in the regions is regarded asthe second chromaticity of the second phosphor sheet 12 in Step S6 ofmeasuring second chromaticities of the second phosphor sheets 12 in FIG.1.

For example, a total of nine regions consisting of a central portion 12d, middle portions 12 e of the four sides, and four corners 12 f of asingle second phosphor sheet 12 are radiated with the excitation lightto measure the chromaticity in each region. The average value of themeasured values is assumed to be the chromaticity (second chromaticity)of the second phosphor sheet 12.

The first chromaticity can be determined in consideration of variationin chromaticity in each first phosphor sheet 11 in the present modifiedexample. The same applies to the second chromaticity. Accordingly,variation in wavelength conversion characteristics of light emitted fromthe light-emitting device can be more effectively reduced.

The positions of the regions of the first phosphor sheet 11 in which thefirst chromaticities are measured are not limited to the above example.The number of the regions of the first phosphor sheet 11 in which thechromaticities are measured is not limited to nine but may be eight orless or ten or more. Similarly, the positions of the regions of thesecond phosphor sheet 12 in which the second chromaticities are measuredand the number of the regions is not limited to the above example.

Second Modified Example of First Embodiment

FIG. 11 is an xy chromaticity diagram for a method of selecting thefirst phosphor sheet and the second phosphor sheet in the presentmodified example.

In the present modified example, a plurality of first phosphor sheets 11are classified into three groups G5, G6, and G7 in ascending order ofthe x value as shown in FIG. 11. For example, a first phosphor sheet 11with an x value of x1 or more and x3 or less is classified as the groupG5, a first phosphor sheet 11 with an x value of greater than x3 and x4or less is classified as the group G6, and a first phosphor sheet 11with an x value of greater than x4 and x2 or less is classified as thegroup G7. The numbers of the first phosphor sheets 11 in the respectivegroups are made as nearly equal as possible. A plurality of secondphosphor sheets 12 are classified into three groups G8, G9, and G10 inascending order of they value. For example, a second phosphor sheet 12with a y value of y1 or more and y3 or less is classified as the groupG8, a second phosphor sheet 12 with a y value of greater than y3 and y4or less is classified as the group G9, and a second phosphor sheet 12with a y value of greater than y4 and y2 or less is classified as thegroup G10. The numbers of the second phosphor sheets 12 in therespective groups are made as nearly equal as possible.

The first phosphor sheet 11 classified as the group G5 is combined withthe second phosphor sheet 12 classified as the group G10, the firstphosphor sheet 11 classified as the group G6 is combined with the secondphosphor sheet 12 classified as the group G9, and the first phosphorsheet 11 classified as the group G7 is combined with the second phosphorsheet 12 classified as the group G8. Variation in chromaticity of lightemitted from the light-emitting device can thus fall within the regionsR5, R6, and R7. As described above, variation in wavelength conversioncharacteristics of light emitted from the light-emitting device can bereduced better in the present modified example than in the firstembodiment.

The first phosphor sheets 11 and the second phosphor sheets 12 areclassified into two groups each in the first embodiment, and the firstphosphor sheets 11 and the second phosphor sheets 12 are classified intothree groups each in the present modified example, but thisclassification is not limiting. The phosphor sheets may be classifiedinto four or more groups.

More generally, the first phosphor sheets 11 can be classified into ngroups G11_1 to G11_n in ascending order of the x value, and the secondphosphor sheets 12 can be classified into n groups G12_1 to G12_n inascending order of the y value, n being an integer of two or more, and kbeing an integer of one or more and nor less. In this case, a firstphosphor sheet 11 classified as a group G11_k is combined with a secondphosphor sheet 12 classified as a group G12_n−k+1. The region ofvariation in the xy chromaticity diagram can thus be reduced to about(1/n) times compared with the case in which the first phosphor sheets 11and the second phosphor sheets 12 are randomly combined.

In this case, the value of n may be equal to the number of the firstphosphor sheets 11 and the number of the second phosphor sheets 12. Thatis, each first phosphor sheet 11 may constitute a group, and each secondphosphor sheet 12 may constitute a group. This case is equivalent to thecase in which a first phosphor sheet 11 is combined with a secondphosphor sheet 12 without grouping.

Specifically, n first phosphor sheets 11 and n second phosphor sheets 12are provided. Let x₁, x₂, . . . , x_(k), . . . , x_(n) be the x valuesof the first phosphor sheets 11 in ascending order, and let y₁, y₂, . .. , y_(k), y_(n), be the y values of the second phosphor sheets 12 inascending order. A first phosphor sheet 11 with an x value of x₁ iscombined with a second phosphor sheet 12 with a y value of y_(n), afirst phosphor sheet 11 with an x value of x₂ is combined with a secondphosphor sheet 12 with a y value of y_(n−1), and a first phosphor sheet11 with an x value of x_(n) is combined with a second phosphor sheet 12with a y value of y₁. Generally, a first phosphor sheet 11 with an xvalue of x_(k) is combined with a second phosphor sheet 12 with a yvalue of y_(n−k+1).

FIG. 12 is an xy chromaticity diagram showing simulation results in thecase in which the first phosphor sheets 11 and the second phosphorsheets 12 are classified and respectively combined.

In the case in which the first phosphor sheets 11 are randomly combinedwith the second phosphor sheets 12, the chromaticities of light emittedfrom the light-emitting devices were scattered two-dimensionally in thexy chromaticity diagram as shown in FIG. 12. On the other hand, in thecase in which the first phosphor sheets 11 and the second phosphorsheets 12 were respectively combined as described above, thechromaticities of light emitted from the light-emitting devices weregathered in a line.

Second Embodiment

FIG. 13 is a flowchart of a method of manufacturing a light-emittingdevice according to the present embodiment.

FIG. 14A and FIG. 14B are schematic cross-sectional views forillustrating the method of manufacturing a light-emitting deviceaccording to the present embodiment.

Steps S1 to S8 are performed similarly to the first embodiment as shownin FIG. 13.

Next, the first phosphor sheet 11 and the second phosphor sheet 12selected in Step S8 are layered to produce a layered sheet 14 in StepS11 in FIG. 13 as shown in FIG. 14A. A plurality of light-emittingelements 13 are disposed on the layered sheet 14. The light-emittingelements 13 are disposed, for example, on an adhesive disposed on thelayered sheet 14.

Next, the layered sheet 14 are divided into a plurality of layeredpieces 14 c in Step S12 in FIG. 13 as shown in FIG. 14B. At this time,one or more light-emitting elements 13 are allowed to be on each layeredpiece 14 c. For example, the layered sheet 14 is divided in units oflight-emitting elements 13. In this case, one light-emitting element 13is disposed on one layered piece 14 c. A plurality of light-emittingdevices 2 according to the present embodiment are thus manufactured at atime. In each light-emitting device 2, the light-emitting element 13 isdisposed on the layered piece 14 c in which the phosphor piece 11 c andthe phosphor piece 12 c are layered.

Third Embodiment

FIG. 15 is a flowchart of a method of manufacturing a light-emittingdevice according to the present embodiment.

FIG. 16 is a schematic cross-sectional view of the light-emitting deviceaccording to the present embodiment.

Steps S1 to S8 are performed similarly to the first embodiment as shownin FIG. 15.

Next, the first phosphor sheet 11 and the second phosphor sheet 12selected in Step S8 are disposed at a position capable of receiving thefirst light L1 emitted from the light-emitting element 13 in Step S13 inFIG. 15 as shown in FIG. 16. For example, a plurality of light-emittingelements 13 are mounted on a mounting board 16. The layered sheet 14 inwhich the first phosphor sheet 11 and the second phosphor sheet 12 arelayered is disposed above the mounting board 16. A light-emitting device3 according to the present embodiment is thus manufactured.

In the light-emitting device 3, the mounting board 16 on which thelight-emitting elements 13 have been mounted may be integrated with thelayered sheet 14 or disposed as a separate member. The layered sheet 14is only required to be disposed at a position where the first light L1emitted from the light-emitting elements 13 enters.

In the above embodiments and modified examples, the x values and the yvalues in the XYZ colorimetric system are used as parameters indicatingthe wavelength conversion characteristics, but these parameters are notlimiting. For example, r values and g values in the RGB colorimetricsystem may be used as parameters indicating the wavelength conversioncharacteristics.

The following describes specific examples of each member used in themethod of manufacturing a light-emitting device according to eachembodiment.

Light-Emitting Element

Examples of the light-emitting element 13 include an LED chip. Thelight-emitting element 13 can have, for example, a semiconductor layeredstructure containing a nitride semiconductor (In_(x)Al_(y)Ga_(1-x-y)N,where 0≤x, 0≤y, and x+y≤1), which can emit ultraviolet to visible light.The peak emission wavelength of the light-emitting element 13 ispreferably 400 nm or more and 530 nm or less, more preferably 420 nm ormore and 490 nm or less, further preferably 450 nm or more and 475 nm orless, in consideration of the light-emission efficiency of thelight-emitting device 1, the excitation spectrum of the phosphor, andthe color mixing performance. The light-emitting device 1 may include asingle light-emitting element 13 or two or more light-emitting elements13. The light-emitting element 13 preferably shows a half-width of 40 nmor less, more preferably 30 nm or less. Light emitted from thelight-emitting element 13 can thus easily have a sharp peak.Accordingly, for example, in the case in which the light-emitting deviceis used for a light source for a liquid-crystal display, theliquid-crystal display can achieve good color reproducibility. Aplurality of light-emitting elements can be electrically connected inseries or in parallel, or in combination of series connections andparallel connections.

The light-emitting element 13 may have any appropriate shape in a planview, and may have a square shape or an elongated rectangular shape in aplan view. The light-emitting element 13 may have a hexagonal shape oranother polygonal shape in a plan view. The light-emitting element 13includes a pair of positive and negative electrodes. The positive andnegative electrodes can be made of gold, silver, copper, tin, platinum,rhodium, titanium, aluminum, tungsten, palladium, nickel, or an alloy ofthese metals. The lateral surfaces of the light-emitting element 13 maybe perpendicular to the upper surface of the light-emitting element 13or may be inclined inward or outward.

First Phosphor Sheet and Second Phosphor Sheet

Materials that transmit light emitted from the light-emitting element 13are used for the base materials of the first phosphor sheets 11 and thesecond phosphor sheets 12. In the present specification, the term“transmit” indicates that the light transmittance at the peak emissionwavelength of the light-emitting element 13 is 60% or more, preferably70% or more, more preferably 80% or more. Examples of the base materialsof the first phosphor sheets 11 and the second phosphor sheets 12include silicone resins, epoxy resins, phenolic resins, polycarbonateresins, acrylic resins, and modified resins of these resins. A siliconeresin or an epoxy resin, which has good resistance to heat and light, isparticularly suitable. Examples of the silicone resin include dimethy1silicone resins, phenyl-methy1 silicone resins, and dipheny1 siliconeresins.

The first phosphor sheets 11 and the second phosphor sheets 12 maycontain light-diffusing particles. Examples of the light-diffusingparticles include silicon oxide, aluminum oxide, zirconium oxide, andzinc oxide. One of these light-diffusing particles can be used singly,or two or more of these light-diffusing particles can be used incombination. Silicon oxide, which has a small linear expansioncoefficient, is particularly preferably used for the light-diffusingparticles. Nanoparticles are preferably used for the light-diffusingparticles. Scattering of light emitted from the light-emitting elementis thus increased, so that the amount of the phosphor to be used can bereduced. The term “nanoparticles” refers to particles having particlediameters of 1 nm or more and 100 nm or less. The particle diameter inthe present specification is mainly defined as D50.

The first phosphor sheets 11 and the second phosphor sheets 12 containphosphors. The phosphors absorb at least a portion of primary lightemitted from the light-emitting element 13 and emit secondary lighthaving wavelengths different from wavelengths of the primary light. Oneof the phosphors described below can be used singly, or two or more ofthe phosphors described below can be used in combination.

Examples of the phosphor include yttrium-aluminum-garnet based phosphors(for example, Y₃(Al,Ga)₅O₁₂:Ce), lutetium-aluminum-garnet basedphosphors (for example, Lu₃(Al,Ga)₅O₁₂:Ce), terbium-aluminum-garnetbased phosphors (for example, Tb₃(Al,Ga)₅O₁₂:Ce), silicate basedphosphors (for example, (Ba,Sr)₂SiO₄:Eu), chlorosilicate based phosphors(for example, Ca₈Mg(SiO₄)₄C1 ₂:Eu), β-SiAlON based phosphors (forexample, Si_(6-z)Al_(z)O_(z)N_(8-z):Eu (0<z<4.2)), SGS based phosphors(for example, SrGa₂S₄:Eu), alkaline earth aluminate based phosphors (forexample, (Ba,Sr,Ca)Mg_(x)Al₁₀O_(17-x):Eu,Mn), α-SiAlON based phosphors(for example, M_(z)(Si,Al)₁₂(O,N)₁₆ (where 0<z≤2, and M is Li, Mg, Ca,Y, or a lanthanoid element except for La and Ce), nitrogen-containingcalcium aluminosilicate based phosphors (for example, (Sr,Ca)AlSiN₃:Eu),and manganese-activated fluoride based phosphors (phosphors representedby the general formula (I) A₂[M_(1-a)Mn_(a)F₆], where “A” is at leastone selected from the group consisting of K, Li, Na, Rb, Cs, and NH₄, Mis at least one element selected from the group consisting of group IVelements and group XIV elements, and “a” satisfies 0<a<0.2). The peakemission wavelength of an yttrium-aluminum-garnet based phosphor can beshifted to a longer wavelength by substituting a portion of Y with Gd.Typical examples of the manganese-activated fluoride based phosphorsinclude manganese-activated potassium fluorosilicate phosphors (forexample, K₂SiF₆:Mn).

INDUSTRIAL APPLICABILITY

The present invention can be used for, for example, a light source of anillumination device or a display device.

The invention claimed is:
 1. A method of manufacturing a light-emittingdevice, the method comprising: providing a plurality of first phosphorsheets; providing a plurality of second phosphor sheets; providing alight-emitting element; selecting a combination of one of the firstphosphor sheets and one of the second phosphor sheets based on awavelength conversion characteristic of each of the first phosphorsheets and a wavelength conversion characteristic of each of the secondphosphor sheets; obtaining a plurality of first phosphor pieces and aplurality of second phosphor pieces from the selected first phosphorsheet and the selected second phosphor sheet; and disposing one of thefirst phosphor pieces and one of the second phosphor pieces on or abovethe light-emitting element.
 2. The method of manufacturing alight-emitting device according to claim 1, the method furthercomprising: a first measurement step of measuring the wavelengthconversion characteristic of each of the plurality of first phosphorsheets; and a second measurement step of measuring the wavelengthconversion characteristic of each of the plurality of second phosphorsheets.
 3. The method of manufacturing a light-emitting device accordingto claim 2, wherein the first measurement step comprises radiating thefirst phosphor sheets with excitation light and measuring a firstchromaticity of mixed light of the excitation light and light emittedfrom each of the first phosphor sheets, and wherein the secondmeasurement step comprises radiating the second phosphor sheets with theexcitation light and measuring a second chromaticity of mixed light ofthe excitation light and light emitted from each of the second phosphorsheets.
 4. The method of manufacturing a light-emitting device accordingto claim 3, wherein, in the step of measuring a first chromaticity, thefirst chromaticity of each of a plurality of regions of each of thefirst phosphor sheets is measured, and an average value of the firstchromaticities of the plurality of regions is used as a firstchromaticity of the first phosphor sheet, and wherein, in the step ofmeasuring a second chromaticity, the second chromaticity of each of aplurality of regions of each of the second phosphor sheets is measured,and an average value of the second chromaticities of the plurality ofregions is used as a second chromaticity of the second phosphor sheet.5. The method of manufacturing a light-emitting device according toclaim 3, the method further comprising: a first classification step ofclassifying the first phosphor sheets according to x value of the firstchromaticity; and a second classification step of classifying the secondphosphor sheets according to y value of the second chromaticity.
 6. Themethod of manufacturing a light-emitting device according to claim 5,wherein, in the first classification step, each of the first phosphorsheets is classified as a first group in a case in which an x value ofthe first phosphor sheet is not greater than a criterion value of the xvalue and is classified as a second group in a case in which the x valueof the first phosphor sheet is greater than the criterion value of the xvalue, and wherein, in the second classification step, each of thesecond phosphor sheets is classified as a third group in a case in whicha y value of the second phosphor sheet is not greater than a criterionvalue of the y value and is classified as a fourth group in a case inwhich the y value of the second phosphor sheet is greater than thecriterion value of the y value.
 7. The method of manufacturing alight-emitting device according to claim 6, wherein, in the selectionstep, the first phosphor sheet classified as the first group is combinedwith the second phosphor sheet classified as the fourth group, and thefirst phosphor sheet classified as the second group is combined with thesecond phosphor sheet classified as the third group.
 8. The method ofmanufacturing a light-emitting device according to claim 6, wherein thecriterion value of the x value is an average value of x values of theplurality of first phosphor sheets, and wherein the criterion value ofthe y value is an average value of y values of the plurality of secondphosphor sheets.
 9. The method of manufacturing a light-emitting deviceaccording to claim 6, wherein the criterion value of the x value is amedian of x values of the plurality of first phosphor sheets, andwherein the criterion value of the y value is a median of y values ofthe plurality of second phosphor sheets.
 10. The method of manufacturinga light-emitting device according to claim 6, wherein the criterionvalue of the x value is an intermediate value between a lower limit andan upper limit of a specification range of the x value of the firstphosphor sheet, and wherein the criterion value of the y value is anintermediate value between a lower limit and an upper limit of aspecification range of the y value of the second phosphor sheet.
 11. Themethod of manufacturing a light-emitting device according to claim 10,wherein chromaticity coordinates of light emitted from thelight-emitting device fall within a hexagonal region with a first point(xp1,y1), a second point (x2,y1), a third point (x2,yp3), a fourth point(xp4,y2), a fifth point (x1,y2), and a sixth point (x1,yp6) at verticesin an xy chromaticity diagram, wherein the specification range of the xvalue of the first phosphor sheet is x1 or more and x2 or less, whereinthe specification range of the y value of the second phosphor sheet isy1 or more and y2 or less, wherein xp1 and xp4 are values greater thanx1 and less than x2, and wherein yp3 and yp6 are values greater than y1and less than y2.
 12. The method of manufacturing a light-emittingdevice according to claim 5, wherein, in the first classification step,the first phosphor sheets are classified into n groups in ascendingorder of the x values, wherein, in the second classification step, thesecond phosphor sheets are classified into n groups in ascending orderof the y values, wherein, in the selection step, one of the firstphosphor sheets classified as a k-th group is combined with one of thesecond phosphor sheets classified as a (n−k+1)th group, wherein n is aninteger of 2 or more, and wherein k is an integer of 1 or more and n orless.
 13. The method of manufacturing a light-emitting device accordingto claim 1, wherein each of the first phosphor pieces comprise: a firstbase material comprising a resin material; and a first phosphor mixed inthe first base material, wherein each of the second phosphor piecescomprise: a second base material comprising a resin material; and asecond phosphor mixed in the second base material, wherein thelight-emitting element emits first light, wherein the first phosphorabsorbs the first light to emit second light, and wherein the secondphosphor absorbs the first light to emit third light.
 14. The method ofmanufacturing a light-emitting device according to claim 13, wherein thefirst light is blue, wherein the second light is red, and wherein thethird light is green.